Abstract
It is known that lower SES is associated with lower working memory capacity, but the mechanisms of this association have not been shown. In this study the authors measured physiological parameters in children at 9 and 13 years of age to see if this could explain future working memory capacity. They created a composite measure indicating chronic stress during childhood. This measure, called “allostatic load”, included blood pressure, cortisol, epinephrine and body mass index, and was measured at age 9 and 13.

When the subjects were 17 their visuo-spatial working memory capacity was measured, and the amount of childhood spent in poverty was estimated. Adolescents who had been rated as spending a larger amount of time in poverty scored about 10% lower on the working memory test. This is consistent with prior finding. The key point was that the researcher could show that this was explained by the allostatic load: childhood allostatic load correlated significantly with working memory in the 17-year olds. After taking out the effect of allostatic load, there was no longer any effect of poverty on working memory. This suggests that it is the chronic stress, rather than other possible effects of childhood poverty, that effect working memory. These results are also consistent with prior finding of how chronic stress affects neurons at the cellular level in a negative way.